The miniaturization of conventional dynamic random access memories (DRAM) has reached its limits. The information is stored in the form of charges, which decrease as the size of the memory cells decreases. When a bit is represented by fewer than approximately 100-1000 elementary charges, it is technically no longer possible to reliably distinguish between the two states of 0 and 1.
For this reason, research is currently underway into resistive random access memories (RRAM), wherein information is written by way of a change in the resistance of the memory material. These memories promise significantly higher data densities than DRAMs and offer the prospect of a universal memory, which also replaces bulk memory because, in principle, they can be designed to be non-volatile. The magazine Nature Materials, Vol. 6, Issue 12 (2008), provides an overview of the current research situation.
The disadvantage of existing resistive memories is that the resistance values thereof vary within a wide range, and the production thereof is difficult to reproduce. As a result, it has not yet been possible to commercialize the technology, even though the technology has been known and under discussion since the 1960s.